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Granule cell raphes and parasagittal domains of Purkinje cells: complementary patterns in the developing chick
1Genetics Department, Howard Hughes Medical Institute, Harvard Medical School, Boston, Massachusetts 02115, USA.
Insights
Developing chick cerebellums show granule cells migrating in streams, forming "granule cell raphes." These correlate with Purkinje cell domains, suggesting a novel interaction crucial for cerebellar patterning.
Area of Science:
- Neuroscience
- Developmental Biology
- Genetics
Background:
- Cerebellar development involves extensive granule cell migration and parasagittal Purkinje cell organization.
- Granule cell migration in the chick cerebellum forms distinct streams and
- Purkinje cells in the developing cerebellum exhibit parasagittal organization.
Purpose of the Study:
- To investigate the spatial and temporal relationship between granule cell migration streams and Purkinje cell organization in the developing chick cerebellum.
- To identify gene expression patterns associated with parasagittal domains in Purkinje cells during cerebellar development.
Main Methods:
- Utilized granule cell markers to observe cell migration patterns in the developing chick cerebellum.
- Analyzed gene expression profiles (Bmp-7, EphA5/Cek-7, EphA4/Cek-8, Drosophila segmentation gene homologs) in Purkinje cells.
- Compared cerebellar development across avian species and with mouse models.
Main Results:
- Granule cells migrate in parasagittal streams, forming
- Purkinje cells segregate into discrete parasagittal domains corresponding to granule cell raphes.
- Domain-specific gene expression in Purkinje cells diminishes as granule cell raphes disappear.
Conclusions:
- Granule cell raphes and Purkinje cell parasagittal domains exhibit spatial and temporal correlations.
- Suggests a novel interaction between granule cells and Purkinje cells during cerebellar development.
- Identifies a potentially critical period for parasagittal patterning in the chick cerebellum.
Abstract:
The extensive migration of granule cells and the parasagittal organization of Purkinje cells are two prominent features of cerebellar development. Using granule cell markers, we observed that the inward migration of a subset of granule cells occurs in streams that appear to be restricted to specific areas in the developing chick cerebellum. These streams are organized into a stereotypical series of parasagittal linear arrays, similar to the "granule cell raphes" described previously by . Similar raphes were found in the developing cerebellum of other avian species but not in the mouse cerebellum. During the period when granule cell raphes are apparent, Purkinje cells appear to be segregated into discrete parasagittal domains, interrupted by Purkinje cell-poor areas that correspond to the granule cell raphes. Purkinje cells in each domain exhibit a domain-specific expression profile of genes, including Bmp-7, EphA5/Cek-7, EphA4/Cek-8, and several chick homologs of Drosophila segmentation genes. From embryonic day 12 (E12) to E15, most of these genes gradually cease to be expressed differentially in parasagittal stripes, concurrent with the disappearance of the granule cell raphes by E15-E16. The spatial and temporal correlations of granule cell raphes and Purkinje cell parasagittal domains suggest a novel interaction between these two cell types and a potentially critical period of parasagittal patterning of the chick cerebellum.